Honey is a powerful attractant for various insect species, and the answer to whether it draws in flies is a clear yes. This common occurrence is rooted in insect biology and the complex chemical makeup of the sweet substance. Flies constantly seek high-energy food sources and optimal breeding grounds, and honey provides a potent combination of both signals. The attraction is an instinctual response to the specific compounds honey releases. Understanding this science can help manage and prevent unwanted fly infestations.
The Chemical Composition That Attracts Flies
The primary attractants in honey are its high concentration of simple sugars, specifically fructose and glucose, which comprise over 70% of its weight. These monosaccharides offer flies an immediate and dense source of metabolic energy, which is a powerful lure for any insect. The low water activity of honey, typically less than 20%, makes it naturally resistant to spoilage, but it also means the sugars are highly concentrated, maximizing the caloric reward for a visiting fly.
A more subtle, yet equally strong, attractant is the presence of volatile organic compounds (VOCs) and organic acids. Honey contains hundreds of different VOCs, including alcohols, aldehydes, and esters, which originate from the nectar of the original flowers or are added during the bees’ enzymatic process. These compounds create the distinct aroma that flies, which rely heavily on their sense of smell, can detect from a distance.
The most significant factor, particularly for certain fly species, is fermentation. While pure, properly stored honey is highly stable due to its low pH and low moisture content, exposure to air or dilution with water allows naturally occurring yeasts to become active. This yeast activity breaks down sugars and produces fermentation byproducts such as ethanol and acetic acid. These compounds are powerful olfactory signals that indicate a decaying, yeast-rich food source many flies actively seek out.
Species Specificity: House Flies Versus Fruit Flies
The term “fly” encompasses numerous species, and their attraction to honey differs based on their feeding habits. Common house flies ( Musca domestica ) are generalist feeders attracted to a broad range of decaying organic matter, including feces and garbage. They are drawn to honey primarily because of its high sugar content and the general food odors released, making it a high-value energy source.
In contrast, fruit flies ( Drosophila melanogaster ) are specialists highly attuned to the scent of fermentation. These insects specifically seek out yeast and alcohol vapors, as these environments are where they lay their eggs and where their larvae can feed on yeast. Consequently, fruit flies are strongly drawn to honey that has begun to ferment, even slightly, or when it is mixed with a fermenting agent like vinegar.
Research shows that while house flies respond to general sweetness, fruit flies respond more intensely to fermentation products like acetic acid and ethanol, often present in or near honey spills. This difference means a jar of pristine honey may attract a house fly seeking a sugar meal, but a sticky spill exposed to air and moisture will be a far more potent lure for fruit flies. The varying chemical signatures of the honey dictate which species will be the primary visitor.
Practical Implications for Storage and Trapping
The biological reasons for honey’s attraction lead directly to practical measures for managing flies. Proper storage is the first line of defense against unwanted fly attention. Honey is hygroscopic, meaning it readily absorbs moisture from the air, which can trigger the fermentation process that produces attractive VOCs.
Storing honey in an airtight container, preferably glass, prevents moisture absorption and blocks the release of aromatic compounds. Cleaning up spills immediately is important, as even a small, sticky residue can quickly absorb ambient moisture and begin to ferment, creating an olfactory beacon for fruit flies within hours.
The mechanism that makes honey a household nuisance can be leveraged for pest control. Honey or sugar water is a proven bait for homemade fly traps. To specifically target fruit flies, the sweet bait is often combined with apple cider vinegar, which provides the strong acetic acid signal that mimics their preferred breeding ground. This combination of sugar for energy and fermentation scent creates a highly effective, targeted lure for trapping flies.